a

GAO

United States Government Accountability Office

Report to the Subcommittee on Tactical 

Air and Land Forces, Committee on 

Armed Services, House of 

Representatives

December 2005 UNMANNED 

AIRCRAFT SYSTEMS

DOD Needs to More 

Effectively Promote 

Interoperability and 

Improve Performance 

Assessments

GAO-06-49
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

www.gao.gov/cgi-bin/getrpt?GAO-06-49.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Sharon Pickup, 

at (202) 512-9619, or pickups@gao.gov. 

Highlights of GAO-06-49, a report to the 

Subcommittee on Tactical Air and Land 

Forces, Committee on Armed Services, 

House of Representatives 

December 2005

UNMANNED AIRCRAFT SYSTEMS

DOD Needs to More Effectively Promote 

Interoperability and Improve Performance 

Assessments 

DOD has achieved certain operational successes using UAS, including 

identifying time-critical targets in Iraq and Afghanistan, and striking enemy 

positions to defeat opposing forces. Some missions effectively supported 

joint operations, and in other cases, the missions were service-specific. 

DOD has encountered challenges which have hampered joint operations at 

times. First, some UAS cannot easily transmit and receive data with other 

communication systems because they are not interoperable. Although DOD 

guidance requires interoperability, detailed standards for interoperability 

have not been developed; DOD has relied on existing, more general 

standards; and the services developed differing systems. For now, U.S. 

forces have developed technical patches permitting transmission but 

slowing data flow, potentially hampering time-critical targeting. Second, 

some sensor payloads cannot be interchangeably used on different UAS 

because DOD has not adopted a payload commonality standard. Some UAS 

missions may have to be delayed if compatible unmanned aircraft and 

payloads are not available. Based on its experience with UAS in Persian 

Gulf operations, U.S. Central Command believes communications 

interoperability and payload commonality problems occur because the 

services’ UAS development programs have been service-specific and 

insufficiently attentive to joint needs. Lastly, the electromagnetic spectrum 

needed to control the flight of certain unmanned aircraft and to transmit 

data is constrained and no standard requiring the capability to change 

frequencies had been adopted because the problem was not foreseen. Thus, 

some systems cannot change to avoid congestion and consequently some 

missions have been delayed, potentially undermining time-critical targeting. 

In addition to the joint operational challenges, inclement weather can also 

hamper UAS operations. Unmanned aircraft are more likely to be grounded 

in inclement weather than manned aircraft and DOD had not decided 

whether to require all-weather capability. While DOD has acknowledged the 

need to improve UAS interoperability and address bandwidth and weather 

constraints, little progress has been made. Until DOD adopts and enforces 

interoperability and other standards, these challenges will likely remain and 

become more widespread as new UAS are developed and fielded. 

DOD’s approach to evaluating UAS joint operational performance has been 

unsound because it was not systematic or routine. DOD has deployed UAS 

before developing a joint operations performance measurement system, 

even though results-oriented performance measures can be used to monitor 

progress toward agency goals. DOD has generally relied on after-action and 

maintenance reports which have useful but not necessarily joint 

performance information. DOD has also relied on short-duration study 

teams for some performance information but had not established ongoing or 

routine reporting systems. Thus, while continuing to invest in UAS, DOD has 

incomplete performance information on joint operations on which to base 

acquisition or modification decisions. In May 2005, U.S. Strategic Command 

began developing joint performance measures. 

Unmanned aircraft systems (UAS) 

consist of an unmanned aircraft; 

sensor, communications, or 

weapons, carried on board the 

aircraft, collectively referred to as 

payloads; and ground controls. 

UAS have been used successfully in 

recent operations, and are in 

increasingly high demand by U.S. 

forces. To meet the demand, the 

Department of Defense (DOD) is 

increasing its investment in and 

reliance on UAS, and often 

deploying them while still in 

development. GAO has previously 

found that DOD’s approach to 

developing and fielding UAS risked 

interoperability problems which 

could undermine joint operations. 

GAO was asked to review (1) UAS 

performance in recent joint 

operations and (2) the soundness 

of DOD’s approach to evaluating 

joint UAS operational performance. 

What GAO Recommends

We are recommending that the 

Secretary of Defense develop and 

apply appropriate joint operating 

standards, and include specific 

performance indicators and 

baselines for analysis and 

systematic information reporting 

and analysis procedures in the new 

performance measurement system 

under development. 

In commenting on a draft of this 

report, DOD fully or partially 

concurred with GAO’s 

recommendations. 
Page i GAO-06-49 Unmanned Aircraft Systems

Contents

Letter 1

Results in Brief 2

Background 5

UAS Have Achieved Certain Mission Successes but DOD Faces 

Emerging Interoperability and Other Challenges on Joint 

Operations 9

DOD’s Approach to Evaluating Joint UAS Performance on 

Operational Deployments Has Been Unsound 18

Conclusions 20

Recommendations for Executive Action 21

Agency Comments and Our Evaluation 23

Appendixes

Appendix I: Scope and Methodology 26

Appendix II: Comments from the Department of Defense 28

Appendix III: GAO Contacts and Staff Acknowledgments 33

Related GAO Products 34

Table Table 1: Bands in the Electromagnetic Spectrum Used by 12 Types 

of Unmanned Aircraft and Sensor Payloads 15

Figure Figure 1: Predator Unmanned Aircraft with Sensor 13

Abbreviations

DOD Department of Defense

UAS unmanned aircraft systems

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Page 1 GAO-06-49 Unmanned Aircraft Systems

United States Government Accountability Office

Washington, D.C. 20548

A

December 13, 2005 Letr

The Honorable Curt Weldon

Chairman

The Honorable Neil Abercrombie

Ranking Minority Member

Subcommittee on Tactical Air

and Land Forces

Committee on Armed Services

House of Representatives

Unmanned aircraft systems (UAS)1 consist of unmanned aircraft; sensors, 

weapons, and communications equipment carried on board the aircraft, 

known as “payloads”; and ground control stations that control the flight of 

the aircraft and receive information collected and transmitted by the 

payloads. UAS have been used successfully in recent military operations 

on intelligence, surveillance, and reconnaissance; and offensive strike 

missions. Due to the successes, U.S. forces are increasingly demanding 

that more UAS be supplied to them, prompting the Department of Defense 

(DOD) to try and rapidly develop and field these emerging technologies. 

Moreover, to meet the demand, DOD has substantially increased its 

investment in these systems from about $363 million in fiscal year 2001 to 

about $2.2 billion in fiscal year 2005, not including supplemental 

appropriations. 

In March 2004, we reported that DOD’s approach to planning for 

developing and fielding UAS did not provide reasonable assurance that its 

investment strategy will facilitate their efficient integration into the force 

structure.2

 We also reported that DOD’s approach increased the risk of 

future interoperability problems, which could undermine joint operations, 

and would likely be insufficient to prevent duplication of effort from one 

service-specific program to another. As a result, we recommended that 

DOD develop a strategic plan for these systems’ development and fielding 

1

Unmanned aircraft systems were previously known as unmanned aerial vehicles. In August 

2005, the Department of Defense began using the new term. We have adopted the new term 

in this report and for clarity will use it when referring to the Unmanned Aircraft Systems 

Planning Task Force, although it was actually known as the Joint Unmanned Aerial Vehicles 

Planning Task Force prior to August 2005. However, we will refer to publications by 

whichever term was used in their titles. 

2

GAO, Force Structure: Improved Strategic Planning Can Enhance DOD’s Unmanned 

Aerial Vehicles Efforts, GAO-04-342 (Washington, D.C.: Mar. 17, 2004).
Page 2 GAO-06-49 Unmanned Aircraft Systems

and assign the UAS Planning Task Force or other appropriate entity within 

DOD with sufficient authority to enforce program direction specified in the 

plan. DOD partially concurred with our recommendation to develop a 

strategic plan and nonconcurred with the recommendation to place an 

entity in charge. DOD’s rationale for nonconcurring was that the 

Undersecretary of Defense (Acquisition, Technology, and Logistics) and by 

extension its UAS Planning Task Force had sufficient authority to develop 

and enforce interoperability and other standards, and that the Joint 

Capabilities Integration and Development System process promoted joint 

war fighting and thus would avoid interoperability problems.3

 In addition, 

DOD has issued guidance requiring interoperable communications 

capabilities in DOD weapons and other systems.

As requested, we reviewed (1) the operational performance of UAS in 

recent joint operations and (2) the soundness of DOD’s approach to 

evaluating joint UAS operational performance. To evaluate the operational 

performance of UAS in recent operations, we examined DOD or service 

regulations, directives, instructions, after-action reports, performance 

evaluations, and other documents. We also met with key DOD and service 

officials to discuss current UAS operational status, future plans, initiatives 

to address emerging challenges, and related issues. To review DOD’s 

approach to evaluating joint UAS performance, we obtained relevant DOD 

directives, instructions, and other documents, and met with DOD and 

service officials to identify the performance measurement systems in place 

and operating. We determined that the data on the numbers and types of 

missions performed by UAS were sufficiently reliable for this review. We 

performed our work from July 2004 to October 2005 in accordance with 

generally accepted government auditing standards. 

Results in Brief DOD has achieved certain operational successes with UAS but 

communications and payload interoperability, electromagnetic spectrum, 

and inclement weather challenges have all emerged to hamper recent joint 

operations or prevent timely UAS employment. On the one hand, U.S. 

forces have used unmanned aircraft and sensor and weapons payloads to 

locate and engage targets in Afghanistan and Iraq since 2002 on both joint

3

The Joint Capabilities Integration and Development System is a collaborative system that 

DOD uses to identify capability gaps and integrated solutions to resolve these gaps. 
Page 3 GAO-06-49 Unmanned Aircraft Systems

and service-specific missions.4 For example, the Air Force used its Global 

Hawk unmanned aircraft to locate 55 percent of time-critical targets to 

suppress enemy air defenses in Iraq in 2003 and the Predator unmanned 

aircraft on over 5,800 sorties or about 80,000 hours of flight on intelligence 

surveillance, reconnaissance, and armed strike missions from 2002 to 2005 

in Iraq and Afghanistan. In addition, in 2004, an Army force used its Hunter 

unmanned aircraft to locate certain antiaircraft artillery; the Air Force sent 

an armed Predator unmanned aircraft to engage the antiaircraft artillery; 

and the Army sent the Hunter back for battle damage assessment. On the 

other hand, interoperability problems have emerged despite the DOD 

guidance requiring interoperability and the 2002 edition of DOD’s 

Unmanned Aerial Vehicles Roadmap 2002-20275

 identifying 

interoperability as a key goal. Specifically, some sensor or 

communications payloads and ground stations cannot easily exchange 

data, sometimes even within a single service, because they were not 

designed to interoperable communication standards. Moreover, the 2002 

Roadmap specifies some communications standards, but the 2005 edition 

of the Roadmap acknowledges that the detailed standards for 

interoperability have not been developed. To use noninteroperable sensors 

or communications payloads and ground stations, U.S. forces have relied 

on technical patches to link them. However, the technical patch process 

can delay receipt of the information by forces needing it, potentially 

preventing time-critical targeting. 

In addition, U.S. forces have also encountered another interoperability 

problem: they are unable to interchangeably use some payloads from one 

type of unmanned aircraft on another, a capability commonly called 

“payload commonality.” DOD has at least six different types of sensor 

payloads, each able to collect different types of information. However, 

some cannot be used interchangeably on differing unmanned aircraft 

because DOD has not adopted a payload commonality standard to make 

them modular and thus permit attachment to most unmanned aircraft. As a 

result, commanders may have to delay missions if the appropriate sensor is 

available but no unmanned aircraft are able to carry it. Interoperability and 

payload commonality problems have arisen because the services’ UAS 

development programs have been service-specific and insufficiently 

4

Joint missions involve UAS from more than one service, whereas service-specific missions 

involve UAS from only one service.

5

Office of the Secretary of Defense, Unmanned Aerial Vehicles Roadmap 2002-2027 

(Washington, D.C.: December 2002).
Page 4 GAO-06-49 Unmanned Aircraft Systems

attentive to joint operational needs, according to U.S. Central Command. 

In addition to interoperability and payload commonality problems, certain 

electromagnetic spectrum frequencies are congested by the large number 

of UAS and other weapons or communications systems using the same 

frequency simultaneously. While some unmanned aircraft, sensor or 

communications payloads, and ground stations can change to different, 

less congested, frequencies, DOD had not required that the capability be 

included on UAS as of the time of our review, and most were consequently 

built without the ability to change. Thus, commanders have had to delay 

certain missions until frequency congestion cleared and DOD 

acknowledges that missions could eventually be delayed or cancelled if the 

problem worsens. 

Unmanned aircraft are more likely to be grounded in inclement weather 

than manned aircraft due in part to their lighter weight. DOD has neither 

required all-weather capability nor evaluated the performance trade-off 

that may arise from developing it even though it established all-weather 

capability as a goal in the 2002 Roadmap. DOD acknowledges that it

(1) did not foresee the rapid technology development experienced with 

unmanned aircraft, sensor or communications payloads, and ground 

stations; (2) has provided unmanned aircraft and payloads rapidly to 

deployed forces to meet forces’ demands for them; and (3) has not always 

adopted standards that might have prevented or mitigated some of these 

problems. While DOD also acknowledged the need to improve UAS 

interoperability and address bandwidth and weather constraints that 

undermine unmanned aircraft operations, little progress has been made. 

Until DOD and the services take steps to ensure that interoperable 

communications and payloads, electromagnetic spectrum reprogramming, 

and all-weather flying standards are developed and enforced for UAS, these 

problems are likely to continue and become more widespread as DOD 

continues to deploy these systems to meet forces’ demands for them. 

DOD’s approach to evaluating UAS joint operational performance has been 

unsound because it is not systematically focused on joint operations and is 

not routine. While results-oriented performance measures can be used to 

monitor progress toward agency goals, DOD has not developed adequate 

indicators of performance on joint operations or baselines against which to 

measure performance for developmental systems that are being used. In 

the meantime, DOD and the services have generally relied on available 

information including after-action and maintenance reports. Nonetheless, 

such information is not necessarily targeted to UAS and does not 

necessarily include reporting on key indicators to measure performance on 
Page 5 GAO-06-49 Unmanned Aircraft Systems

joint operations, since the indicators have not been identified, and does not 

include baselines against which to apply the indicators to permit insight 

into performance. DOD has acknowledged that it tried to meet combat 

forces’ increasing demands for UAS and consequently deployed the 

systems as quickly as possibly but without first developing the 

performance indicators and baselines. DOD had begun to develop 

performance measures by the time of our review. Performance reporting 

has also not been routine. Instead, DOD and the services have relied on 

short-duration study teams rather than ongoing processes for obtaining 

performance information on joint operations. While these teams have 

produced some useful information, the approach does not routinely 

provide information that would permit systematic performance 

assessments since the teams are not permanently established and did not 

employ consistent study parameters. DOD has acknowledged the need for 

systematic joint performance reporting and in May 2005 tasked U.S. 

Strategic Command responsibility for developing appropriate performance 

measures and reporting systems. Until DOD develops a systematic 

approach to UAS performance measurement and reporting on joint 

operations, it will have incomplete information on which to base 

acquisition or system modification decisions.

To address the emerging challenges that have hampered joint operations or 

prevented effective employment of UAS, we are making recommendations 

to the Secretary of Defense to develop or adjust communications 

interoperability, payload commonality, and electromagnetic spectrum 

reprogramming standards; ensure that the new performance measurement 

system includes indicators that can be used to assess progress in 

overcoming communications interoperability, payload commonality, and 

electromagnetic spectrum challenges; and also ensure that the new 

performance measurement system includes other appropriate performance 

indicators for collection, baselines against which to apply the indicators, 

and a systematic means to collect joint operations performance 

information and report it to organizations that develop and field UAS. In 

written comments on a draft of this report, DOD partially or fully 

concurred with our recommendations and indicated that it had initiated 

actions to address them. DOD’s comments and our evaluations of them are 

provided later in this report.

Background DOD defines UAS as a powered aircraft that does not carry a human 

operator; can be land-, air-, or ship-launched; uses aerodynamic forces to 

provide lift; can be autonomously or remotely piloted; can be expendable 
Page 6 GAO-06-49 Unmanned Aircraft Systems

or recoverable; and can carry a lethal or nonlethal payload. Generally, UAS 

consist of the aircraft; a flight control station; information and retrieval or 

processing stations; and, sometimes, wheeled land vehicles that carry 

launch and recovery platforms. UAS carry a payload including sensors for 

intelligence, surveillance, or reconnaissance to provide real-time 

intelligence to battlefield commanders. When used on an intelligence, 

surveillance, or reconnaissance mission, generally, the aircraft carries a 

sensor payload capable of detecting heat, movement, or taking 

photographs or video of ground-based targets. This information is then 

transmitted to ground stations or satellites via a communications payload 

for retransmission to forces needing the information to support operations. 

Unmanned aircraft can also be armed for offensive strike missions and be 

used to attack ground-based targets. UAS require adequate intra- or 

intertheater communications capabilities using the electromagnetic 

spectrum to permit operators to control certain aircraft, and also permit 

communications equipment to transmit the information obtained by the 

sensor payload to ground commanders or other users.

Effective joint operations are critical because combatant commanders 

operate in a joint environment by applying military force appropriate for 

their operational circumstance using the unique capabilities of each of the 

services. In a changing security environment, joint operations are 

becoming more important given the complex nature of military operations. 

This importance is being driven by the combatant commands’ need to 

combine the capabilities of multiple services to address the global threat, 

as well as the growing interdependence of capabilities among the services. 

Moreover, effective joint operations permit combatant commanders to 

leverage the capabilities associated with each service to accomplish 

operational missions. As with manned aircraft, UAS provide another 

capability that can be applied by combatant commanders in joint 

operations. 

Evolution of UAS 

Development and Use

Initially, UAS were seen as complementary systems that augmented 

existing war fighting capabilities. However, UAS are also evolving into 

more significant roles, for which they can provide primary capability. For 

example, the Global Hawk UAS may eventually replace the U-2 

reconnaissance aircraft, and the Unmanned Combat Aerial System may 

eventually perform electronic warfare missions currently performed by the 

EA-6 Prowler aircraft as well as offensive deep strike missions. Moreover, 

UAS are figuring prominently in plans to transform the military into a more 

strategically responsive force and are expected to be an integral part of this 
Page 7 GAO-06-49 Unmanned Aircraft Systems

information-based force. For example, the Army is developing the Future 

Combat System and a new generation of unmanned aircraft and other 

systems to enable information to flow freely across the battlefield. 

Since 2001, DOD has significantly increased its planned expenditure for 

UAS and associated systems, and, more recently, the systems have 

continued to be heavily used in Afghanistan and Iraq. In fact, over 10 

different types of UAS have been used in Afghanistan and Iraq. According 

to the UAS Planning Task Force, as of August 2005, DOD had 

approximately 1,500 unmanned aircraft in Iraq and Afghanistan. In 

addition, the budget request for UAS grew significantly between fiscal 

years 2001 and 2005, from about $363 million to about $2.2 billion, and 

further growth is likely. These figures do not include any supplemental 

appropriations. 

Fewer than half of the UAS in Iraq and Afghanistan at the time of our report 

had reached full-rate production or initial operating capability. They were 

still considered developmental, and consequently were covered by DOD 

Directive 5000.1, The Defense Acquisition System and DOD Instruction 

5000.2, Operation of the Defense Acquisition System, both issued in May 

2003.6

 The directive mandates that systems, units, and forces shall be able 

to provide and accept data, information, materiel, and services to and from 

other systems, units, and forces, and shall effectively interoperate with 

other U.S. forces, among other things. The instruction implements the 

directive and is intended to provide DOD officials with a framework for 

identifying mission needs and technology to meet the needs, as the basis 

for weapons system acquisitions. Finally, the 2002 Roadmap emphasizes 

the need for interoperable unmanned aircraft and payloads by identifying a 

number of existing standards that are to be complied with in systems’ 

development in such areas as common data links, interoperable data links 

for video systems, and electromagnetic spectrum frequencies that should 

be used for data transmission under a variety of circumstances.7

6

DOD Directive 5000.1, The Defense Acquisition System, May 12, 2003 and DOD Instruction 

5000.2, Operation of the Defense Acquisition System, May 12, 2003.

7

In August 2005, DOD issued an updated version of the roadmap. See Office of the Secretary 

of Defense, Unmanned Aircraft Systems Roadmap 2005-2030 (Washington, D.C.: August 

2005).
Page 8 GAO-06-49 Unmanned Aircraft Systems

Prior GAO Reviews of 

DOD’s Planning for 

Developing and Fielding 

UAS

In March 2004, we reported that DOD’s approach to planning for 

developing and fielding UAS does not provide reasonable assurance that its 

investment will facilitate efficient integration into the force structure and 

avoid interoperability problems, although DOD had taken some steps to 

improve UAS program management. For example, in 2001, DOD 

established the Joint Unmanned Aerial Vehicles Planning Task Force (now 

known as the UAS Planning Task Force) in the Office of the Undersecretary 

of Defense (Acquisition, Technology, and Logistics). To communicate its 

vision and promote commonality of UAS, the Task Force published the 

2002 Unmanned Aerial Vehicle Roadmap, which described current 

programs, identified potential missions, and provided guidance on 

emerging technologies. While the Roadmap demonstrated some elements 

of a strategic plan, neither it nor other key documents represented a 

comprehensive strategic plan to ensure that the services and DOD agencies 

develop systems that complement each other, perform all required 

missions, and avoid duplication. Moreover, the Task Force served in an 

advisory capacity to the Undersecretary, but had little authority to enforce 

program direction. For their part, service officials told us that they 

developed service-specific planning documents to meet their own needs 

and operational concepts without considering those of other services or 

the Roadmap. In consequence, we concluded that without a strategic plan 

and an oversight body with sufficient authority to enforce program 

direction, DOD risked interoperability problems, which could undermine 

joint operations. Thus, in our 2004 report, we recommended that DOD 

establish a strategic plan and assign an office authority and responsibility 

to enforce program direction communicated in the plan to promote joint 

operations.

DOD partially concurred with our recommendation to establish a strategic 

plan and nonconcurred with our recommendation to assign an office with 

authority and responsibility to enforce program direction. DOD asserted 

that the Undersecretary had sufficient authority to integrate UAS into joint 

operations and that the Task Force had been established to promote 

payload commonality, develop and enforce interface standards, and ensure 

multiservice coordination. Moreover, DOD indicated that the Joint 

Capabilities Integration and Development System process focuses on 

developing integrated joint warfighting capabilities and thus would avoid 

interoperability problems that we believed were likely. 
Page 9 GAO-06-49 Unmanned Aircraft Systems

UAS Have Achieved 

Certain Mission 

Successes but DOD 

Faces Emerging 

Interoperability and 

Other Challenges on 

Joint Operations

DOD has achieved certain operational successes with UAS including 

collecting intelligence with unmanned aircraft sensor payloads and 

conducting offensive strike missions with weapons payloads in 

Afghanistan and Iraq. Nonetheless, U.S. forces employing UAS have 

encountered certain communications and payload interoperability 

problems (called payload commonality problems), electromagnetic 

spectrum constraints, and inclement weather groundings of unmanned 

aircraft during recent operations. While DOD has acknowledged the need 

to improve UAS interoperability and address bandwidth and weather 

constraints that undermine unmanned aircraft operations, little progress 

has been made.

UAS Have Played an 

Integral Role in Mission 

Accomplishments

DOD has achieved certain operational successes from its use of a variety of 

unmanned aircraft and their sensor, communications, and armaments 

payloads. In operations in Iraq or Afghanistan since 2002, U.S. forces have 

used UAS in integral roles on intelligence, surveillance, reconnaissance, 

and offensive strike joint or service-specific missions. For example:

• The Air Force used its Predator unmanned aircraft with sensor or 

armaments payloads on over 5,800 sorties or totaling more than 80,000 

hours of flight on a variety of intelligence, surveillance, and 

reconnaissance; close air support; armed strike; and other missions in 

Iraq and Afghanistan from 2002 through 2005.8

 For example, the 

Predator’s sensor and communications payloads have provided video 

images to ground forces to support their operations or to strike enemy 

targets with Hellfire missiles. 

• Certain Air Force units used the Global Hawk unmanned aircraft’s 

sensor payloads to identify 55 percent of the time-critical targets to 

defeat enemy air defenses in Iraq in March and April 2003. To enhance 

joint operations, the Air Force developed procedures and tactics to 

allow the Global Hawk’s sensor payloads to provide more direct support 

to ground force missions. 

• In 2004, an Army force used its Hunter unmanned aircraft and sensor 

payload to locate an enemy antiaircraft artillery weapon that had been 

firing at coalition force aircraft. Then the Air Force sent a Predator 

8

This is the latest information available at the time of our review.
Page 10 GAO-06-49 Unmanned Aircraft Systems

armed with a Hellfire missile to attack the enemy weapon. Within 

minutes of the Predator strike, the Army unit sent its Hunter back to 

transmit information needed for battle damage assessment. 

• In 2004, an Army force operating an I-Gnat unmanned aircraft in Iraq 

detected a potential ambush of Marine Corps forces and the Army unit 

used information from the I-Gnat’s sensor payload to successfully adjust 

mortar fire onto the enemy position. 

• Recently, the Air Force, Army and Marine Corps forces have used their 

unmanned aircraft and their sensor and communications payloads to 

locate numerous targets in Iraq and Afghanistan to permit U.S. forces to 

destroy the targets. 

UAS Interoperability 

Remains a Challenge

While achieving certain successes with the use of unmanned aircraft and 

their payloads, certain interoperability challenges have also emerged 

during recent operations despite certain DOD directives requiring 

interoperability and the emphasis on interoperability in the 2002 Roadmap. 

First, DOD Directive 5000.1 specifies that systems, units, and forces shall 

be able to provide and accept data and information to and from other 

systems and shall effectively interoperate with other U.S. forces. Second, 

the Roadmap specifies five data standards for formatting data, a 

communication standard to ensure adoption of a common data link, and a 

variety of file transfer, physical media, and other standards applicable to 

unmanned aircraft or their sensor and communications payloads. 

However, the 2005 edition of the Roadmap indicates that the detailed 

standards for interoperability have not been developed. In effect, the 

absence of such standards has led to the development of UAS that are not 

interoperable. In operations in Afghanistan and Iraq, interoperability 

problems have emerged. Specifically, during operations, DOD has learned 

that unmanned aircraft sensor and communications payloads and ground 

stations were not designed to common data standards and thus are not 

interoperable, even within a single service in certain circumstances. For 

example:

• Army forces operate both the Shadow and Hunter unmanned aircraft 

and associated ground stations but discovered that these systems are 

not interoperable. Specifically, while the Shadow’s sensor and 

communications payload is able to transmit information to its own 

ground station, it is unable to transmit to a Hunter ground station. 

Similarly, the Hunter’s sensor and communication payloads are able to 
Page 11 GAO-06-49 Unmanned Aircraft Systems

transmit to a Hunter ground station but not Shadow’s. Onward 

transmission to forces needing the information is equally constrained if 

they do not have compatible equipment for receiving the information. 

As a result, the Army has missed an opportunity to effectively leverage 

the technology inherent in either system for the benefit of operational 

forces that need the information. At the time of our review, the Army 

had begun an initiative to make the Shadow and Hunter unmanned 

aircraft ground stations compatible with either aircraft. 

When communication systems are incompatible, operating forces may be 

prompted to operate their own UAS, thus increasing the numbers of 

systems operating in the same area. To permit the sharing of tactical 

intelligence obtained by unmanned aircraft sensor payloads, the services or 

combatant commands have developed certain technical patches permitting 

compatibility but slowing data transmission. As we pointed out in 2003, in 

some cases, DOD needs hours or days to transmit information to multiple 

services.9

 However, slow intelligence data transmission can undermine U.S. 

forces’ ability to attack time-critical targets or allow the targets to escape. 

U.S. Central Command acknowledges that timely data dissemination is 

critical to combat operations. 

Communications interoperability problems are a long-standing problem. In 

2001, we reported that each of the military services plans, acquires, and 

operates systems to meet its own operational concepts but not necessarily 

the requirements of joint operations in spite of the DOD directive requiring 

interoperability.10 In our 2004 unmanned aerial vehicle report, we reported 

that the services engaged in little coordination in developing their 

unmanned aerial vehicle roadmaps and that they did not view the UAS 

Planning Task Force’s 2002-2027 Roadmap as a strategic plan or an 

overarching architecture for integrating UAS into the force structure. In 

the absence of adequately developed and implemented standards and in 

contravention of the DOD guidance, the services have continued to develop 

their unmanned systems to their own standards, but without regard to the 

others’ standards. At the same time, DOD continues to develop and field 

UAS without adjusting the standards, likely causing the problem to become 

even more widespread. Moreover, the UAS used in current operations 

9

GAO, Defense Acquisitions: Steps Needed to Ensure Interoperability of Systems That 

Process Intelligence Data, GAO-03-329 (Washington, D.C.: Mar. 31, 2003).

10GAO, Joint Warfighting: Attacking Time Critical Targeting, GAO-02-204R (Washington, 

D.C.: Nov. 30, 2001).
Page 12 GAO-06-49 Unmanned Aircraft Systems

were built before the Joint Capabilities Integration and Development 

System became fully operational and thus has had little impact on the 

problem. Consequently, the information collected cannot always be 

quickly transmitted to users needing it, undermining joint operations and 

potentially leading to future costly initiatives to modify existing unmanned 

aircraft, sensors and communications payloads, and ground stations to 

overcome interoperability problems. 

In addition to communications interoperability problems, payload 

interoperability (commonly referred to as “payload commonality”) 

problems also exist. DOD has developed at least six different sensor 

payloads each able to collect different types of information. These sensor 

payloads are attached to an unmanned aircraft and flown over operational 

areas to observe activity of interest on the ground in a target area and to 

transmit observations to ground or air forces or other users as tactical 

intelligence. As an example, figure 1 displays a Predator unmanned aircraft 

with a sensor payload attached underneath.
Page 13 GAO-06-49 Unmanned Aircraft Systems

Figure 1: Predator Unmanned Aircraft with Sensor 

However, many sensor payloads can be attached to only one type of 

unmanned aircraft because DOD has not adopted a payload commonality 

standard even though this problem was identified nearly 20 years ago. As a 

result, commanders may have to delay missions if the appropriate sensor is 

available but no unmanned aircraft is able to carry it. We discussed this 

problem in 1988 when we reported that DOD had not adequately 

emphasized payload commonality for unmanned aircraft and that Congress 

had stressed the need for DOD to consider payload commonality in 1985.11 

The 2002 Roadmap acknowledged the need for sensor payload 

commonality where practical, but limited progress has been made.

In addition to the flexibility inherent in the communications standards, 

according to U.S. Central Command based on its experience in Persian Gulf 

11GAO, Unmanned Vehicles: Assessment of DOD’s Unmanned Aerial Vehicle Master Plan, 

GAO/NSIAD-89-41BR (Washington, D.C.: Dec. 9, 1988).

Source: Air Force.
Page 14 GAO-06-49 Unmanned Aircraft Systems

operations, unmanned aircraft development has been service-centric and 

lacks an overarching employment doctrine to shape development to 

achieve aircraft and sensor interoperable communications and payload 

commonality. Furthermore, a Joint Forces Command official told us that 

combatant commanders can not take full advantage of the dissimilar 

unmanned aircraft or the sensor payload data produced due to the 

interoperability problems. 

Congested Electromagnetic 

Spectrum Has Hampered 

UAS Operational 

Effectiveness

Unmanned aircraft and their sensor, armaments, and communications 

payloads depend on reliable access to the electromagnetic spectrum.12 

However, the spectrum is increasingly constrained, potentially 

undermining joint operations by requiring delays in an unmanned aircraft 

flight or, if the problem worsens, cancellation. Unmanned aircraft 

operators use the electromagnetic spectrum to maintain contact with the 

aircraft to control its flight, fire its weapons if armed, and receive 

information collected by the sensor payloads. Certain spectrum 

frequencies are sometimes referred to as bands and the amount of the 

spectrum needed to permit transmission of information is referred to as 

bandwidth. DOD officials told us that more bandwidth is needed to 

transmit video and other information obtained by sensor payloads than to 

maintain flight control of the aircraft. Numerous weapons also use 

electromagnetic spectrum and share it with UAS but they can interfere with 

each other during operations if they operate on the same frequency at the 

same time.

The military services have experienced bandwidth capacity constraints, 

limiting both the number of UAS and other systems that can be effectively 

operated simultaneously and the amount of available data that can be 

transmitted from the unmanned aircraft communications payload. For 

example, insufficient bandwidth limits U.S. forces’ ability to download 

video and radar images via satellite from more than one aircraft at a time. 

As a result, data transmission and relay are delayed, undermining U.S. 

forces’ ability to engage time-critical targets and possibly permitting the 

target to escape, unless alternative information sources are available on a 

timely basis. Army officials informed us that data link limitations are due 

primarily to frequency congestion. Table 1 displays the bands used by 12 

different unmanned aircraft or models of unmanned aircraft for flight 

12The electromagnetic spectrum refers to the range of radio frequencies used in wireless 

communication.
Page 15 GAO-06-49 Unmanned Aircraft Systems

control and sensor payload data transmission. As shown in the table, 

several UAS rely on the C-band for their data transmission capability, and 

only 2 of the 12 UAS can be reprogrammed to another band.

Table 1: Bands in the Electromagnetic Spectrum Used by 12 Types of Unmanned 

Aircraft and Sensor Payloads

Source: DOD.

The 2002 Roadmap established a goal of modifying the Army’s Shadow 

UAV to permit it to operate a common tactical data link in Ku-band and not 

the more congested C-band. This goal had not been met at the time of our 

review and the Shadow unmanned aircraft still operated in C-band. 

Similarly, the 2002 Roadmap established a goal of moving the Air Force’s 

Predator unmanned aircraft video sensor payload from C-band to Ku-band 

for line of sight operations. However, the goal had not been met at the time 

of our report.

Moreover, the problem cannot be easily overcome without potentially 

costly modifications to existing systems because DOD has not required 

unmanned aircraft or sensor payloads to be reprogrammable from one 

band to another and therefore has not established such standards. As a 

result, most have been designed and built without the flexibility to operate 

in differing frequencies or bands to avoid congested frequencies, thus 

sometimes preventing timely information transmission or delaying their 

flight without interfering with or experiencing interference from other UAS 

or other weapons systems. 

Inclement Weather Limits 

Some Unmanned Aircraft 

Operations 

Unmanned aircraft are more likely to be grounded by inclement weather 

than manned aircraft due in part to their lighter weight. Dust storms, 

strong winds, rain, or icing prevent some unmanned aircraft from flying, 

thus denying U.S. forces critically needed information unless alternative 

data collection or offensive strike capabilities are available. Specifically, 

Band Flight control Data transmission

C Band 3 5

Ku Band 3 3

C or Ku Band 2 2

Other 4 2

Total 12 12
Page 16 GAO-06-49 Unmanned Aircraft Systems

winds up to 80 miles per hour in Iraq and Afghanistan have reduced the 

availability of most unmanned aircraft and dust storms have undermined 

the use of some sensor payloads. Moreover, the 2002 Roadmap indicates 

that icing has been a primary factor in two accidents involving the Hunter 

unmanned aircraft and three crashes of the Predator unmanned aircraft. 

The Roadmap established a goal to incorporate all-weather capabilities 

into future UAS. However, little progress has been made because DOD has 

not adopted standards for all-weather capability to be considered in 

development, despite the Roadmap’s stating the goal. As a result, systems 

have been developed without it. At the same time, according to a UAS 

Planning Task Force official, developing unmanned aircraft with allweather capabilities may result in some degradation in performance, such 

as a reduced flying range. At the time of our review, DOD had not 

determined whether all-weather capability was worth the trade-off of 

potentially degraded performance.

DOD Has Made Little 

Progress in Addressing the 

Challenges

While DOD has acknowledged the need to improve UAS interoperability 

and address bandwidth and weather constraints that undermine unmanned 

aircraft operations, little progress has been made. On the one hand, to 

begin to address the problems, DOD has taken a number of steps as listed 

below:

• In August 2005, DOD issued an updated version of its roadmap, entitled 

2005 Unmanned Aircraft Systems Roadmap, to guide acquisition and 

interoperability. Among other things, the 2005 Roadmap establishes the 

goal of enhancing joint service collaboration as a means to improve joint 

operations. 

• At the time of our review, the Office of the Secretary of Defense was 

preparing an action plan to address a number of shortfalls including 

interoperability and other problems within U.S. Central Command’s area 

of responsibility, although the plan was limited to just this command and 

would not necessarily solve the problems that UAS might encounter 

elsewhere.

• DOD plans to reemphasize the role that the Joint Capabilities 

Integration and Development System could play in all new UAS 

developments by trying to ensure that DOD develops systems to support 

joint operations, achieve commonality to the extent practical, and 

identify gaps in DOD’s ability to carry out its warfighting missions.
Page 17 GAO-06-49 Unmanned Aircraft Systems

• U.S. Joint Forces Command has developed certain initiatives to improve

UAS interoperability by conducting experiments to demonstrate aircraft 

modifications and new concepts of operations, although such 

modifications can be costly.

In addition, on June 1, 2005, DOD’s Joint Requirements Oversight Council 

established a new Joint Unmanned Aerial Vehicle Center of Excellence and 

a Joint Unmanned Aerial Vehicle Overarching Integrated Process Team. 

The Joint Unmanned Aerial Vehicle Overarching Integrated Process Team 

has subsequently been renamed the Joint Unmanned Aircraft Systems 

Material Review Board. These joint forums will help the services manage 

development of new UAS or modifications to existing UAS, and they will 

help the services to develop new or revised concepts of operations for 

more effective use. At the same time, the UAS Planning Task Force will try 

to ensure that the services’ UAS acquisition programs are coordinated, and 

a Task Force representative is to be a member of the Joint Overarching 

Integrated Process Team. DOD views these changes as means to more 

effectively manage service UAS programs. While these changes appear to 

be steps in the right direction, it is too early for us to tell if they will solve 

the interoperability and other problems that we identified.

Furthermore, payload commonality, interoperability of communications 

and data transmission systems, and inclement weather flying capabilities 

that we identified as impacting recent operations, had been identified 

previously as problems already occurring or likely to occur. First, our 1988 

unmanned aerial vehicle report indicated that DOD had not adequately 

emphasized payload commonality for these aircraft. Second, our 2001 

report found interoperability problems due to the services’ continued 

practice of acquiring systems to support their own operations but not 

necessarily that of the other services. Third, DOD’s guidance requires 

interoperability but the detailed standards have not been developed. 

Lastly, the 2002 edition of the Roadmap identified the need to improve 

interoperability of communications systems for UAS and also identified 

inclement weather capability as a problem undermining UAS operations 

and established goals to address it. Despite all the emphasis, problems 

related to communications and payload interoperability, and all-weather 

capability problems remain. DOD acknowledges that it (1) did not foresee 

the rapid technological development experienced with unmanned aircraft, 

sensor or communications payloads, and ground stations; (2) has provided 

unmanned aircraft and payloads rapidly to deployed forces to meet forces’ 

demands for them; and (3) has not always adopted new or enforced 

existing standards that might have prevented or mitigated some of these 
Page 18 GAO-06-49 Unmanned Aircraft Systems

problems. As a result, while DOD has issued a directive, instructions, 

guidance, and roadmaps, and established at least five different 

organizations to promote UAS interoperability and address other 

unmanned aircraft and payload developmental needs, no organization has 

or has exercised sufficient authority to enforce program direction, or 

ensure that the standards and guidance are in concurrence. As a result, the 

services continued to develop and field these systems without fully 

complying with the interoperability requirements stated in key guidance or 

addressing known payload commonality problems.

DOD’s Approach to 

Evaluating Joint UAS 

Performance on 

Operational 

Deployments Has Been 

Unsound 

DOD’s approach to evaluating joint UAS performance on operational 

deployments is unsound because it has not implemented a systematic 

approach to evaluating such performance. Instead, DOD has relied on 

systems for evaluating performance that are not focused on joint 

operations and are nonroutine, and as a result the department has little 

assurance that the information that has been collected represents the key 

performance indicators needed to assess performance on joint operations. 

DOD Lacks Performance 

Indicators to Assess Certain 

Joint UAS Performance

DOD has not implemented a systematic approach to evaluating joint UAS 

performance on operational deployments. As we previously noted in our 

2004 report, the Government Performance and Results Act’s strategic 

planning framework specifies that results-oriented performance measures 

can be used to monitor progress toward agency goals and that such 

performance measurements should be developed and used to monitor 

progress. At the time of our report, DOD was only beginning to decide on 

key indicators of performance that would be used to assess unmanned 

aircraft, payload, and ground station performance on joint operations. To 

date, DOD has relied on service-specific information that addressed certain 

UAS performance. For example, some forces filed after-action reports and 

maintenance reports addressing UAS performance. While producing some 

useful information, these reports have not necessarily been specifically 

targeted to joint UAS operations, nor do they systematically identify key 

indicators for collection which could be used to develop joint operational 

performance baselines and permit performance measurement against the 

baseline. Thus, DOD has little assurance that the information that has been 

collected represents the key performance indicators needed to assess joint 

operations performance.
Page 19 GAO-06-49 Unmanned Aircraft Systems

DOD officials told us that they have tried to keep pace with operating 

forces’ demands for more unmanned aircraft and their payloads, and 

therefore the services have deployed them while still under development 

within the DOD acquisition system. These deployments have often 

occurred before identification of key performance indicators that would 

need to be collected to be used to evaluate performance. In effect, the 

services have bought and deployed unmanned aircraft, sensor and 

communications payloads, and ground stations and tried to evaluate their 

effectiveness all at the same time. On the one hand, this has permitted 

DOD to provide operating forces with new capabilities represented by the 

aircraft and their payloads. On the other hand, it has also resulted in DOD 

and the services sometimes learning of joint performance problems based 

on reporting from actual operations only if after-action reports or other 

reporting mentioned the problem. Nonetheless, without appropriate 

performance measures and baselines against which to assess performance 

on joint operations, even anecdotal information can have limited utility 

because officials are less likely to be able to assess the magnitude of the 

problem, or even become aware of it if no reports identify it.

DOD has acknowledged the need to develop specific performance 

indicators for unmanned aircraft and their payloads on joint operations and 

had begun to develop them at the time of our report. First, the Army 

recently began an initiative to develop performance indicators and a 

baseline against which to assess performance. However, while this 

approach may produce useful information on which to assess the 

performance of Army-operated unmanned aircraft, payloads, and ground 

stations, it was not designed to address joint performance. The other three 

services had not started to develop specific performance indicators and 

baselines for unmanned aircraft at the time of our review. Second, in May 

2005, DOD assigned U.S. Strategic Command responsibility for the 

development of joint performance indicators but the effort was just getting 

started at the time of our review. 

DOD’s UAS Joint 

Performance Reporting Has 

Not Been Routine

In addition to anecdotal performance reporting, DOD has not established 

routine performance reporting mechanisms for UAS operations but instead 

has relied on sometimes short-duration study teams to gather relevant joint 

operational performance information. For example, in November 2004, 

DOD established a group known as a “Tiger Team” to identify opportunities 

for improving the joint operational effectiveness of UAS. However, this 

team was established on a temporary basis and had a limited mission to 

identify improvements only in the U.S. Central Command area of 
Page 20 GAO-06-49 Unmanned Aircraft Systems

responsibility. The Tiger Team did identify a number of areas needing 

improvement. For example, it determined that forces in the region need 

Full Motion Video capability to provide images of actual events as they 

occur. The team also determined that a need exists to address 

electromagnetic spectrum limitations hampering UAS operations. 

However, the team identified the electromagnetic spectrum problem only 

after the UAS had been deployed and U.S. forces had tried to use them on 

operational missions. In addition, also in 2004, another DOD shortduration study team evaluated the operational performance of the Shadow 

unmanned aircraft. Lastly, the Army conducted a one-time comprehensive 

review of the effectiveness of its UAS in theaters of operations. While 

these teams developed useful performance information, the approach does 

not represent a systematic or long-term means to obtain joint UAS 

performance information since the teams are not permanently established 

and they did not use consistent study parameters.

Finally, even in the instances where some ongoing processes were used, 

the information obtained was relevant only on a service-specific but not a 

joint basis. For example, the Marine Corps uses its Operational Advisory 

Group process to determine needed improvements in its UAS operations. 

While this group has developed useful information that may assist the 

Marine Corps in enhancing its ability to effectively use UAS in operations, 

the information developed is likely to have limited utility for joint 

operations.

DOD acknowledges that the speed with which unmanned aircraft, 

payloads, communications, and associated technology are being 

developed, along with the imperative to provide emerging technologies 

quickly to operating forces, have resulted in the deployment of 

developmental systems before adequate performance reporting systems 

have been established. Consequently, while the systems are being 

successfully used in overseas operations, DOD does not have reasonable 

assurance that it is well informed on opportunities to further enhance the 

ability of operational forces to take advantage of UAS capabilities.

Conclusions DOD has achieved certain operational successes with UAS but certain 

challenges have also emerged that have hampered joint operations or 

prevented effective employment of UAS. These challenges are caused by 

the limited attention paid to interoperability standards for UAS and the lack 

of detailed interoperability standards. Development and implementation of 

appropriate interoperability, payload commonality, and other standards 
Page 21 GAO-06-49 Unmanned Aircraft Systems

help to ensure that such problems are addressed during development and 

any problems are fixed prior to deployment. Moreover, until DOD assesses 

the extent to which a lack of detailed standards undermines the purpose of 

the broad standards by allowing development of noninteroperable systems 

and enforces common standards among the services, problems are likely to 

continue and possibly be repeated and made more widespread as new 

unmanned aircraft, sensor and communication payloads, ground stations, 

and related equipment are developed and fielded. In addition, costly 

modifications might be needed later. 

The unsoundness in the approach DOD has taken to assessing joint UAS 

performance in operational deployments was due to a lack of accepted 

performance indicators and a routine system for collecting performance 

information. Until DOD develops specific indicators of UAS joint 

operational performance, establishes appropriate baselines against which 

to measure performance, and communicates which indicators operating 

forces should systematically collect and report to appropriate users, DOD 

will lack reasonable assurance that it is adequately informed on UAS 

performance on joint operations. Moreover, DOD may also be poorly 

informed as to its progress in addressing interoperability and other 

problems and may therefore be less likely to avoid the same problems in 

future UAS development and fielding.

Lastly, in our 2004 report, we recommended that DOD establish a strategic 

plan and an office with sufficient authority to enforce program direction to 

avoid interoperability problems and for other purposes. In nonconcurring 

with our recommendation to assign an office with sufficient authority to 

enforce program direction, DOD indicated that the UAS Planning Task 

Force and Joint Capabilities Integration and Development System had 

sufficient authority and would address interoperability, payload 

commonality, and other problems. However, these problems persist. 

Consequently, we continue to believe that sustained management attention 

is warranted. Without such attention, DOD continues to risk undercutting 

the benefit of its continued investment in UAS. Consequently, we continue 

to believe that our prior recommendation has merit, but we are not 

reiterating it because DOD indicated that it will not implement it.

Recommendations for 

Executive Action

To address the challenges emerging in joint operations, we recommend that 

the Secretary of Defense direct the Undersecretary of Defense 

(Acquisition, Technology, and Logistics), the Chairman of the Joint Chiefs 
Page 22 GAO-06-49 Unmanned Aircraft Systems

of Staff, the service secretaries, and other appropriate organizations to 

work together to take the following four actions

• develop or adjust communications interoperability standards and 

electromagnetic frequency reprogramming capabilities standards and 

ensure that they are applied to new or modified unmanned aircraft, 

sensor and communications payloads, ground stations, and related 

equipment; 

• develop sensor and other payload commonality standards where 

practical and enforce such standards when modifying existing 

unmanned aircraft or payloads and developing new ones;

• develop appropriately detailed UAS interoperability standards; and 

• determine whether unmanned aircraft need all-weather flying 

capabilities, identify any performance degradation associated with allweather flying capabilities, and obtain all-weather capabilities where 

appropriate.

To improve joint operational performance reporting, we recommend that 

the Secretary of Defense direct the Commander of the U.S. Strategic 

Command to ensure that the performance measurement system being 

developed by the command at a minimum

• measures how effectively UAS perform their missions by identifying 

quantifiable goals and comparing results with desired outcomes;

• identifies the specific performance indicator information that needs to 

be collected to adequately assess joint performance;

• develops indicators that assess communications and payload 

interoperability, and the extent to which electromagnetic spectrum 

congestion is undermining joint operations;

• establishes baselines and applies the identified indicators against the 

baselines to gauge success in joint UAS performance; and

• develops a way to systematically collect identified performance 

information and routinely reports it to organizations that develop and 

field UAS. 
Page 23 GAO-06-49 Unmanned Aircraft Systems

Agency Comments and 

Our Evaluation

DOD provided written comments on a draft of this report. These 

comments are reprinted in their entirety in appendix II. We made five 

recommendations and DOD fully or partially concurred with them. It also 

provided technical comments, which we incorporated into our report as 

appropriate.

First, DOD concurred with our recommendation for the appropriate DOD 

organizations to work together to develop or adjust communications 

interoperability standards and electromagnetic frequency reprogramming 

capabilities standards and ensure that they are applied to new or modified 

unmanned aircraft, sensor and communications payloads, ground stations, 

and related equipment. In concurring, DOD indicated that it recognized the 

utility of communications interoperability and the need to improve this 

capability and will direct the services to use common frequencies and data 

links to enhance communications interoperability. 

Second, in partially concurring with our recommendation to develop and 

enforce sensor and other payload commonality standards where practical, 

DOD commented that it does not typically focus on payload 

interchangeability. Instead, DOD pointed out that unmanned aircraft 

payload procurement is a service responsibility and is dependent on 

service mission requirements, unmanned aircraft physical design 

limitations, and rapid technological evolution. Our report recognizes that 

it is not practical for all unmanned aircraft sensors and payloads to be 

common due to the various sizes of some aircraft and we worded our 

recommendation accordingly. 

Third, DOD fully concurred with our recommendation that the appropriate 

DOD organizations work together to develop appropriately detailed UAS 

interoperability standards. DOD indicated that the UAS Roadmap 2005-

2030 released in August 2005 discusses the preferred framework, 

methodology, and standards for achieving UAS interoperability. DOD 

outlined a number of actions that it has taken to address UAS 

interoperability standards, including ratifying a North Atlantic Treaty 

Organization Standards Agreement aimed at achieving joint and combined 

interoperability. The Joint Chiefs of Staff has tasked the newly formed 

Joint UAS Material Review Board and Joint UAV Center of Excellence to 

provide recommendations for continuing to improve UAS interoperability. 

Fourth, DOD fully concurred with our recommendation to determine 

whether unmanned aircraft need all-weather flying capabilities, identify 
Page 24 GAO-06-49 Unmanned Aircraft Systems

any performance degradation associated with all-weather capabilities, and 

obtain all-weather capabilities where appropriate. DOD commented that 

combatant commanders should expect UAS to support operations in 

diverse weather conditions. Further, DOD indicated that as UAS 

capabilities improve, the weather conditions these systems will need to 

operate in will also increase. However, DOD also points out that it is not 

cost effective to expect all classes of unmanned aircraft to have an allweather capability. We agree. The intention of our recommendation is for 

DOD to determine those UAS for which all-weather capabilities are cost 

effective and to add such capabilities when appropriate. 

Finally, DOD partially concurred with our recommendation that U.S. 

Strategic Command ensure that the performance measurement system 

being developed at a minimum includes quantifiable goals, performance 

baselines, systematic collection procedures, measures of communications 

and payload interoperability, and performance indicators against which to 

measure performance. DOD indicated that the U.S. Strategic Command 

has drafted a Joint Functional Component Concept of Operations that 

includes metrics to gauge the force’s ability to meet intelligence, 

surveillance, and reconnaissance requirements. Moreover, DOD stated that 

in conjunction with the services, intelligence community, combatant 

commanders, and other DOD organizations, this action would facilitate not 

only the evaluation of UAS performance but would enable DOD to have the 

necessary information available to assess such factors as UAS 

requirements, mission accomplishment, UAS capabilities, and customer 

satisfaction. DOD also pointed out that the performance measures are in 

development and will require service participation to define the specific 

data and methodology which will result in useful information. While we 

acknowledge that these actions should address many of the data elements 

that we believe are necessary to evaluate UAS, we continue to believe that 

effective communications, interoperability, and avoidance of frequency 

congestion are important contributors to the success of joint operations. 

Therefore, we continue to believe that DOD should ensure that, at a 

minimum, the U.S. Strategic Command includes the data elements we 

recommended in its performance measurement system. In addition, we 

agree that other organizations including the services, should participate in 

the development of this measurement system if appropriate. 

We are sending copies of this report to other appropriate congressional 

committees, the Secretary of Defense, the secretaries of the Army, the 

Navy, and the Air Force; the Commandant of the Marine Corps; the 
Page 25 GAO-06-49 Unmanned Aircraft Systems

Chairman of the Joint Chiefs of Staff; and the Director, Office of 

Management and Budget. We will also make copies available to other 

interested parties upon request. In addition, the report will be available at 

no charge on the GAO Web site at http://www.gao.gov.

If you or your staff have any questions about this report, please call me at 

(202) 512-9619 or email at pickups@gao.gov. Contact points for our Office 

of Congressional Relations and Public Affairs may be found on the last 

page of this report. The GAO contact and key contributors are listed in 

appendix III.

Sharon Pickup

Director, Defense Capabilities

and Management
Page 26 GAO-06-49 Unmanned Aircraft Systems

Appendix I

Scope and Methodology AAppenednxidexiIs

To evaluate the operational performance of unmanned aircraft systems 

(UAS) in recent operations, we examined the Department of Defense 

(DOD) regulations, directives, and instructions as well as service guidance 

and documentation on UAS. We met with key DOD and service officials, 

including those from the UAS Planning Task Force and UAS program 

managers, to discuss the current status and future plans for these systems. 

We reviewed the Unmanned Aerial Vehicles Roadmap 2002-2027 because 

this document establishes an overall DOD management framework for 

developing and employing UAS DOD-wide and the update, 2005 

Unmanned Aircraft Systems Roadmap. During discussion and visits with 

DOD and service officials, we obtained and reviewed DOD and service 

analyses, briefings, and summary reports describing each of the UAS used 

in supporting recent combat and combat support operations. This included 

obtaining detailed information on current and future UAS operational 

capabilities. Additionally, we obtained information on the numbers and 

types of missions performed by UAS, as well as the methods used by the 

services to evaluate UAS performance in accomplishing those missions. To 

assess the reliability and types of missions provided to us by DOD, we (1) 

interviewed knowledgeable officials about the processes for collecting and 

maintaining the data and (2) reviewed the data for completeness and 

reasonableness by comparing it to other sources of information. We 

determined that the data were sufficiently reliable for the purposes of this 

review. DOD and service officials also provided specific examples of 

operational successes and emerging challenges. We discussed actions 

taken and processes used by DOD and service officials and the Joint 

Capabilities Integration and Development System to address identified 

challenges. We also held discussions with Joint Staff officials to discuss 

their efforts to address joint UAS issues via the Tiger Team.

The specific military activities that we visited and/or obtained written 

responses to questions from include the following:

• Office of the Undersecretary of Defense (Acquisition, Technology, and 

Logistics) and its Joint UAS Planning Task Force; Washington, D.C.; 

• Headquarters, Department of the Army; Washington, D.C.;

• U.S. Army Redstone Arsenal, Huntsville, Alabama;

• U.S. Marine Corps, Systems Command, Quantico, Virginia;
Appendix I

Scope and Methodology

Page 27 GAO-06-49 Unmanned Aircraft Systems

• U.S. Navy Naval Sea Systems Command, Naval Air Station Patuxent 

River, Maryland;

• U.S. Air Force Air Combat Command Directorate of Requirements, 

Langley Air Force Base, Virginia;

• U.S Air Force, Air Force Material Command, Wright Patterson Air Force 

Base Dayton, Ohio;

• U.S. Joint Forces Command, Norfolk, Virginia;

• U.S. Central Command, MacDill Air Force Base, Tampa, Florida;

• U.S. Special Operations Command, MacDill Air Force Base, Tampa, 

Florida; 

• U.S. Joint Staff, Washington, D.C., and

• U.S Strategic Command, Omaha, Nebraska.

We also obtained documents describing the mission and planned 

operations of the new Joint Unmanned Aerial Vehicle Center of Excellence 

and Joint Unmanned Aerial Vehicle Overarching Integrated Process Team.

To assess the soundness of DOD’s approach to evaluating UAS operational 

performance, we interviewed DOD and service officials to discuss the 

criteria and processes used to assess performance. We also obtained and 

reviewed DOD and Army UAS Operations Assessments to identify issues 

and concerns regarding performance. Additionally, we held discussions 

with U.S. Strategic Command officials to obtain information on the status 

of their efforts to establish measures for assessing joint UAS performance. 

We also held discussions with service officials to determine the extent to 

which they are required to capture information on the use and performance 

of UAS in their existing lessons-learned systems. Finally, we obtained and 

reviewed DOD and service specific UAS or unmanned aerial vehicle 

roadmaps.

We performed our work from July 2004 to October 2005 in accordance with 

generally accepted government auditing standards. 
Page 28 GAO-06-49 Unmanned Aircraft Systems

Appendix II

Comments from the Department of Defense ApendxiI
Appendix II

Comments from the Department of Defense

Page 29 GAO-06-49 Unmanned Aircraft Systems
Appendix II

Comments from the Department of Defense

Page 30 GAO-06-49 Unmanned Aircraft Systems
Appendix II

Comments from the Department of Defense

Page 31 GAO-06-49 Unmanned Aircraft Systems
Appendix II

Comments from the Department of Defense

Page 32 GAO-06-49 Unmanned Aircraft Systems
Page 33 GAO-06-49 Unmanned Aircraft Systems

Appendix III

GAO Contacts and Staff Acknowledgments ApendxiI

GAO Contact Sharon L. Pickup, (202) 512-9619

Acknowledgments In addition to the person named above, Brian J. Lepore, Assistant Director; 

Harry E. Taylor, Jr.; Patricia F. Albritton; Jeanett H. Reid; Elisha T. Matvay; 

Robert B. Brown; Cheryl A. Weissman; Ron La Due Lake; and Kenneth E. 

Patton also made major contributions to this report.
Page 34 GAO-06-49 Unmanned Aircraft Systems

Related GAO Products

Unmanned Aerial Vehicles: Improved Strategic and Acquisition 

Planning Can Help Address Emerging Challenges. GAO-05-395T. 

Washington, D.C.: March 9, 2005.

Unmanned Aerial Vehicles: Changes in Global Hawk’s Acquisition 

Strategy Are Needed to Reduce Program Risks. GAO-05-6. Washington, 

D.C.: November 5, 2004.

Unmanned Aerial Vehicles: Major Management Issues Facing DOD’s 

Development and Fielding Efforts. GAO-04-530T. Washington, D.C.: 

March 17, 2004.

Force Structure: Improved Strategic Planning Can Enhance DOD’s 

Unmanned Aerial Vehicles Efforts. GAO-04-342. Washington, D.C.: March 

17, 2004.

Nonproliferation: Improvements Needed for Controls on Exports of 

Cruise Missile and Unmanned Aerial Vehicles. GAO-04-493T. Washington, 

D.C.: March 9, 2004.

Nonproliferation: Improvements Needed to Better Control Technology 

Exports for Cruise Missiles and Unmanned Aerial Vehicles. GAO-04-175. 

Washington, D.C.: January 23, 2004.

Defense Acquisitions: Matching Resources with Requirements Is Key to 

the Unmanned Combat Air Vehicle Program’s Success. GAO-03-598. 

Washington, D.C.: June 30, 2003.

Unmanned Aerial Vehicles: Questionable Basis for Revisions to Shadow 

200 Acquisition Strategy. GAO/NSIAD-00-204. Washington, D.C.: 

September 26, 2000.

Unmanned Aerial Vehicles: Progress of the Global Hawk Advanced 

Concept Technology Demonstration. GAO/NSIAD-00-78. Washington, D.C.: 

April 25, 2000.

Unmanned Aerial Vehicles: DOD’s Demonstration Approach Has 

Improved Project Outcomes. GAO/NSIAD-99-33. Washington, D.C.: August 

30, 1999.
Related GAO Products

Page 35 GAO-06-49 Unmanned Aircraft Systems

Unmanned Aerial Vehicles: Progress toward Meeting High Altitude 

Endurance Aircraft Price Goals. GAO/NSIAD-99-29. Washington, D.C.: 

December 15, 1998.

Unmanned Aerial Vehicles: Outrider Demonstrations Will Be Inadequate 

to Justify Further Production. GAO/NSIAD-97-153. Washington, D.C.: 

September 23, 1997.

Unmanned Aerial Vehicles: DOD’s Acquisition Efforts. GAO/T-NSIAD-97-

138. Washington, D.C.: April 9, 1997.

Unmanned Aerial Vehicles: Hunter System Is Not Appropriate for Navy 

Fleet Use. GAO/NSIAD-96-2. Washington, D.C.: December 1, 1995.

Unmanned Aerial Vehicles: Performance of Short-Range System Still in 

Question. GAO/NSIAD-94-65. Washington, D.C.: December 15, 1993.

Unmanned Aerial Vehicles: More Testing Needed Before Production of 

Short-Range System. GAO/NSIAD-92-311. Washington, D.C.: September 4, 

1992.

Unmanned Aerial Vehicles: Medium Range System Components Do Not 

Fit. GAO/NSIAD-91-2. Washington, D.C.: March 25, 1991.

Unmanned Aerial Vehicles: Realistic Testing Needed Before Production of 

Short-Range System. GAO/NSIAD-90-234. Washington, D.C.: September 28, 

1990.

Unmanned Vehicles: Assessment of DOD’s Unmanned Aerial Vehicle 

Master Plan. GAO/NSIAD-89-41BR. Washington, D.C.: December 9, 1988.

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